Question

我想问一下，我有可能为多个级别创建查询预测和标准吗？我有2个模型类：

@Entity  
@Table(name = "person")  
public class Person implements Serializable {
    @Id
    @GeneratedValue
    private int personID;
    private double valueDouble;
    private int valueInt;
    private String name;
    @OneToOne(cascade = {CascadeType.ALL}, orphanRemoval = true)
    @JoinColumn(name="wifeId")
    private Wife wife;
       /*   
        *  Setter Getter    
        */
}


@Entity 
@Table(name = "wife")  
public class Wife implements Serializable {

    @Id
    @GeneratedValue     
    @Column(name="wifeId")
    private int id;
    @Column(name="name")
    private String name;
    @Column(name="age")
    private int age;            
    /*
     *  Setter Getter
     */       
}

我的标准API：

ProjectionList projections = Projections.projectionList(); 
projections.add(Projections.property("this.personID"), "personID");
projections.add(Projections.property("this.wife"), "wife");
projections.add(Projections.property("this.wife.name"), "wife.name");

Criteria criteria = null; 
criteria = getHandlerSession().createCriteria(Person.class); 
criteria.createCriteria("wife", "wife", JoinType.LEFT.ordinal()); 
criterion = Restrictions.eq("wife.age", 19);  
criteria.add(criterion); 
criteria.setProjection(projections);
criteria.setResultTransformer(Transformers.aliasToBean(Person.class)); 
return criteria.list();

我希望，我可以使用指定的wife属性条件查询Person，并指定返回resultSet。所以我使用Projections获取指定的返回resultSet

我想返回personID，姓名（Person），姓名（Wife）。 API我必须如何使用，我更喜欢使用Hibernate Criteria API。

这一次，我使用上面的代码来获取我的预期结果，但它会抛出异常并显示错误消息： Exception in thread "main" org.hibernate.QueryException: could not resolve property: wife.name of: maladzan.model.Person，以及我的Restrictions.eq("wife.age", 19);是否适合让有妻子19岁的人作为她的年龄值？

由于

Answer 1

AFAIK使用aliastobean变压器不可能投射多个深度。你的选择是

创建展平的数据传输对象（DTO）
自己在内存中填充生成的人
实现您自己的resulttransformer（类似于选项2）

选项1如下所示：

Criteria criteria = getHandlerSession().createCriteria(Person.class)
    .createAlias("wife", "wife", JoinType.LEFT.ordinal())
    .add(Restrictions.eq("wife.age", 19)); 
    .setProjection(Projections.projectionList()
        .add(Projections.property("personID"), "personID")
        .add(Projections.property("name"), "personName")
        .add(Projections.property("wife.name"), "wifeName"));
    .setResultTransformer(Transformers.aliasToBean(PersonWifeDto.class));

return criteria.list();

Answer 2

我写了ResultTransformer，这完全是这样做的。它的名称为AliasToBeanNestedResultTransformer，请在github上查看。

Answer 3

谢谢Sami Andoni。我能够使用您的AliasToBeanNestedResultTransformer进行微小修改以适应我的情况。我发现嵌套变换器不支持字段在超类中的场景，所以我对它进行了增强，以便在你预测的类的类继承层次结构中查找最多10级深的字段：

    public Object transformTuple(Object[] tuple, String[] aliases) {

        ...


                if (alias.contains(".")) {
                    nestedAliases.add(alias);

                    String[] sp = alias.split("\\.");
                    String fieldName = sp[0];
                    String aliasName = sp[1];

                    Class<?> subclass = getDeclaredFieldForClassOrSuperClasses(resultClass, fieldName, 1);
...
}

其中getDeclaredFieldForClassOrSuperClasses（）定义如下：

private Class<?> getDeclaredFieldForClassOrSuperClasses(Class<?> resultClass, String fieldName, int level) throws NoSuchFieldException{
    Class<?> result = null;
    try {
        result = resultClass.getDeclaredField(fieldName).getType();
    } catch (NoSuchFieldException e) {
        if (level <= 10){
        return getDeclaredFieldForClassOrSuperClasses(
                resultClass.getSuperclass(), fieldName, level++);
        } else {
            throw e;
        }
    }
    return result;
}

此嵌套属性的Hibernate投影如下所示：

Projections.projectionList().add( Property.forName("metadata.copyright").as("productMetadata.copyright"));

我投射的课程看起来像这样：

public class ProductMetadata extends AbstractMetadata {
...
}

public abstract class AbstractMetadata {
...   
   protected String copyright;
...
}

Answer 4

而不是创建Data Transfer Object (DTO)
在projectionlist进行以下更改，它将对您有用。

    ProjectionList projections = Projections.projectionList(); 
    projections.add(Projections.property("person.personID"), "personID");
    projections.add(Projections.property("person.wife"), "wife");
    projections.add(Projections.property("wife.name"));

    Criteria criteria = null; 
    criteria = getHandlerSession().createCriteria(Person.class,"person").createAlias("person.wife", "wife"); 
    criterion = Restrictions.eq("wife.age", 19);  
    criteria.add(criterion); 
    criteria.setProjection(projections);
    criteria.setResultTransformer(Transformers.aliasToBean(Person.class)); 
    return criteria.list();

复杂的Hibernate预测

4 个答案: